A device for delivering pressurizedair in a controlled quantity to a controlled location. At its most simple terms a bellows is a container which is deformable in such a way as to alter its volume which has an outlet or outlets where one wishes to blow air.

That concertina was a wonder in its way. The handles that was on it first was wore out long ago, and he'd made new ones of braided rope yarn. And the bellows was patched in more places than a cranberry picker's overalls.